The present invention generally relates to electric conductors and more particularly, to an electric conductor used for wiring of high-frequency signal transmission circuits in video appliances such as a television (TV) set, a cathode ray tube (CRT), etc. or audio appliances and a method of manufacturing the electric conductor.
In these electronic appliances, when signals are not transmitted accurately without phase difference, ambiguous images and obscure sounds are produced in the video appliances and the audio appliances, respectively.
Conventionally, an annealed copper wire, into which tough pitch copper (pure copper containing 200 to 500 ppm of oxygen) or oxygen-free copper (pure copper containing substantially no oxygen) is subjected to cold working and then, is annealed for its softening so as to be recrystallized, or, in some cases, a hard drawn copper wire subjected to only cold working, or a copper wire obtained by plating one of the annealed copper wire and the hard drawn copper wire with tin, etc. has been used as the above described electric conductor.
However, the known copper wires have not necessarily been advantageous for accurate transmission of signals on the following grounds. Namely, the annealed copper wire has excellent flexibility and therefore, is used frequently. However, since crystal grains of the annealed copper wire are usually distributed in a configuration similar to that of a regular system due to the recrystallization upon the annealing, the number of grain boundaries traversed by electric current flowing in the longitudinal direction of the wire increases. Therefore, it is considered that defective transmission of signals, e.g., phase difference of the signals, especially, high-frequency component signals is greatly caused by the grain boundaries.
Meanwhile, the hard drawn copper wire has a crystal structure extending in the longitudinal direction of the wire in a fibrous manner as compared with the annealed copper wire. Since the number of grain boundaries traversed by electric current flowing in the longitudinal direction of the wire apparently becomes smaller than that of the annealed copper wire, the hard drawn copper wire is less likely to be adversely affected by the grain boundaries than the annealed copper wire. However, density of electron hole (point defect) and density of dislocation (line defect) in the hard drawn copper wire are far larger than those of the annealed copper wire and non-uniform electron density unsuitable for electric conduction is formed in many portions of the hard drawn copper wire, thereby resulting in possible phase difference of the high-frequency component signals.